Introduction

One of the most important achievements of modern developmental psychology has been to draw attention to the universal and astonishing capacity of young children to mind-read: it appears incontrovertible that by four years of age, children interpret behaviour in terms of agents' mental states (Wellman, 1990; Astington et al., 1988). In John Morton's (1989) chilling phrase, they mentalise: they convert the behaviour they see others perform, or that they perform themselves, into actions driven by beliefs, desires, intentions, hopes, knowledge, imagination, pretence, deceit, and so on. Behaviour is instantly, even automatically, interpreted in terms of what the agent might be thinking, or planning, or wanting. What makes this developmental achievement of such interest is that it raises a learnability problem: how on earth can young children master such abstract concepts as belief (and false belief) with such ease, and at roughly the same time the world over? After all, mental states are unobservable, and have complex logical properties, as Leslie (1987), following Frege (1892) points out. If anything, we should have expected that mental state concepts should be bafflingly difficult to acquire, and yet even the most unremarkable child seems to understand them – without any explicit teaching. Reading minds seems to come naturally, whilst reading words seems to require a considerable amount of instruction.